1. Field of the Invention
The present invention relates to a stapler having moveable clinchers.
2. Related Art
In a large-sized stapler for binding many sheets or a stapler in which legs of a staple are linearly bent on a backside of a sheet along the backside of the sheet, a clincher mechanism that bends the legs of the staple after the staple penetrates the sheets may be adopted.
The clincher mechanism has a pair of clinchers that can rotate to correspond to two legs of the staple having penetrated the sheets and a clincher support part that rotates the clinchers in a pushing up direction by an ascent and descent operation of the clinchers. The clincher mechanism also has a slider that performs lock and lock-release at a standby position of the clinchers and a link that transmits movement of a handle to the slider (for example, refer to Patent Documents 1 and 2).
Patent Document 1: JP-Y-06-016664
Patent Document 2: JP-A-2009-072846
In the conventional clinchers, when the staple penetrates the sheets by pressing a handle, movement of the link is transmitted to the slider and the lock of a clincher holder to which the clinchers are rotatably attached is released.
When the lock of the clincher holder is released, the clincher holder is pressed and descends by the force of pressing the sheets. As the clincher holder descends, the pair of clinchers is pushed up and rotated upward by the clincher support part, thereby bending the legs of the staple. Then, when the force of pressing the handle is released, the clincher holder is returned to the standby position together with the clinchers.
In the configuration of bending the legs of the staple by the rotating operation of the pair of left and right clinchers, when there are many sheets to be bound and a protruding amount of the legs from the backside of the sheet is small, the legs collide with clincher surfaces at upper sides of rotating fulcrum points of the clinchers.
At this state, when the clinchers rotate, as movement of starting to bend the legs, a force of lifting up the legs outward is applied. Thereby, it is not possible to bend the legs of the staple inward.
In order to solve the above problem, it is necessary to adopt a staple having longer legs so as to enable the legs to protrude from the backside of the sheet by a predetermined amount or larger even when there are many sheets to be bound. However, when the staple having longer legs is used, it is necessary to widen a width of a staple crown as the increased length of the legs so that the bound legs do not protrude beyond the width of the staple crown in a case where the smaller number of sheets is bound by the staple having longer legs.
Since it is also necessary to widen the width of the staple crown, a width of a magazine is increased and the whole apparatus is enlarged.
Also, since it is necessary to change a type of the staple depending on the number of sheets to be bound, the usability for a user is poor.
Further, in the stapler moving the clinchers, the clincher holder having the clinchers attached thereto is applied with the force of pushing up the same by a return spring. The slider that locks the ascent and descent of the clincher holder is typically provided at the rear of the clinchers.
In the large staplers, the handle is also configured to extend to the front of the clinchers so as to apply a large force, in many cases. Also, the return spring that pushes up the clincher holder is attached to the front of the clinchers with avoiding the slider.
Therefore, the clincher holder is applied with the force of pushing up the front side thereof by the return spring. Also, due to the load that is applied when the staple penetrates the sheets, the clincher holder is applied with the force of pushing up the rear side thereof by the slider. Hence, the clincher holder is inclined forward about the slider serving as a fulcrum.
Thereby, according to the conventional stapler, the rearward inclined state of the clincher holder at the standby state is changed to the forward inclined state by the load that is applied when the staple penetrates the sheets. However, when the inclination of the clincher holder is changed before and after the penetrating load is applied, a position of the sheets is deviated. As a position of the sheets is deviated, the legs are deviated in the front-rear direction in the sheets during the penetration, so that the legs may not penetrate the sheets and thus the sheets may not be bound. Also, in the stapler disclosed in Patent Document 2, a clincher frame and a clincher cover are enlarged, so that the cost is increased.
Further, in the stapler where the staple having long legs can be used, if the legs are linearly bent, the legs may overlap each other when the number of sheets to be bound is small. Hence, in order to avoid the overlapping of the legs, a configuration is adopted in which a pair of clinchers is slightly offset in a front-rear direction. As disclosed in Patent Document 2, recesses are formed on upper surfaces of the clinchers, thereby guiding the legs upon the bending.
However, in the configuration where the clinchers are formed with the recesses to guide the legs, it is necessary to secure a thickness of a convex part between the recess and the recess, so that it is not possible to narrow the interval between the legs. When an interval between the legs is wide, a user may feel the finishing poor. Also, when the clinchers are formed with the recesses by the cutting processing and the like, the cost of parts is increased.
Further, in the configuration where the legs of the staple are bent by the rotation operation of the pair of clinchers, the clinchers are not applied with the urging force in the rotating direction. Hence, at the state where the clincher unit is at the standby position, the clinchers are rotated downward and are pushed up by the clincher support part.
Even when the clinchers are rotated downward at the standby position, it does not influence on the operation of bending the legs of the staple. However, at this state, a space is formed at the inside of the clincher holder, so that the foreign matters are introduced therein. Also, the outward appearance may be deteriorated.